Graphic File formats:

 

As designers, we are probably most concerned with TIFF, JPEG, PNG, GIF, BMP, EPS, PSD and PDF file formats.

 

Additional references for designers include:

Graphics file  size comparisons: One important consideration is, of course, graphic file size. This example gives a useful comparison of the standard graphic files.

Image File Formats – Which to Use? : Good discussion GIF, JPG and PNG from a designer’s perspective.

Imaging Strategies: Detailed discussion of imaging strategies. Should be useful for any designer. Includes incorporation of vector files.

A Manual of Graphic File Formats:  Lengthy, detailed article which includes a great many of the graphic file formats available from various programs and systems. Very good background for the serious designer.

 

TIFF: (Tagged Image File Format)  A widely used bitmapped graphics file format developed by Aldus and Microsoft that handles monochrome, gray scale, 8-and 24-bit color.  TIFF allows for customization, and several versions have been created, which does not guarantee compatibility between all programs. TIFF files are compressed using several compression methods.  LZW provides ratios of about 1.5:1 to 2:1.  Ratios of 10:1 to 20:1 are possible for documents with lots of white space using ITU Group III and IV compression methods (fax. (Computer Desktop Encyclopedia)  (Back to Top)

 

JPEG (Joint Photographic Experts Group)  Pronounced "jay-peg."  An ISO/ITU standard for compressing still images that became very popular due to its high compression capability.  Using discrete cosine transform, it provides lossy compression (you lose some data from the original image) with ratios up to 100:1 and higher.It depends on the image, but ratios of 10:1 to 20:1 may provide little noticeable loss.  The more the loss can be tolerated, the more the image can be compressed.  Compression is achieved by dividing the picture into tiny pixel blocks, which are halved over and over until the ratio is achieved.  JPEG can be implemented in software or hardware, the latter providing sufficient speed for realtime, on-the-fly compression.  C-Cube Microsystems introduced the first JPEG chip.

JPEG++ is an extension to JPEG from Storm Technology, Mountain View, CA, that allows picture areas to be selectable for different ratios.  For example, the background could be compressed higher than the foreground image.

JPEG uses the JPEG File Interchange Format, or JFIF.  File extensions are .JPG or .JFF.  M-JPEG and MPEG are variations of JPEG used for full-motion digital video.  See JPE file, MPEG and GIF. (Computer Desktop Encyclopedia) (Back to Top)

 

PNG (Portable Network Graphics)  A bitmapped graphics file format endorsed by the World Wide Web Consortium.  It is expected to eventually replace the GIF format, because there are lingering legal problems with GIFs.  CompuServe owns the format, and Unisys owns the compression method.  In addition, GIF is a very basic graphics format that is limited to 256 colors (8-bit color).

PNG provides advanced graphics features such as 48-bit color, including an alpha channel, built-in gamma and color correction, tight compression and the ability to display at one resolution and print at another. (Computer Desktop Encyclopedia) (Back to Top)

 

GIF (Graphics Interchange Format)  A popular bitmapped graphics file format developed by CompuServe.  Pronounced "giff" by Macintosh users and "jiff" by PC users, GIF supports 8-bit color (256 colors) and is widely used on the Web, because the files compress well.  GIFs include a color table that includes the most representative 256 colors used.  For example, a picture of the forest would include mostly greens.  This method provides excellent realism in an 8-bit image.

There are two versions of GIF: the original GIF87a and the subsequent GIF89a, both named after their year of introduction.  GIF89a allows one of the colors to be made transparent (see alpha channel) and take on the background color of the underlying page or window.  GIF89a also supports animated GIFs, which are GIF frames displayed one after the other to simulate movement (see animated GIF).

GIFs and JPEGs: Both GIF and JPEG images are widely used on the Web and are supported by all Web browsers and other Web software.  The choice is usually a simple one.  Charts, screen shots and technical drawings are compressed best as GIFs, and GIFs only hold up to 256 colors (8-bit color).  Most all photographs are better as a JPEG, which supports 24-bit color and has the option of several compression levels (the choice depends on how much degradation you can tolerate).  If you save a scanned image in both formats, you may see a dramatic difference in file size between them.

The Patent Issue: The GIF format uses the LZW compression algorithm, which was patented by Unisys, and publishers of applications that read and write GIF87a and GIF89a images were required to obtain a license and pay royalties to the company.  For example, publishers of Web browsers and image editors were licensees.  The Unisys patents expired in June 2003 for the U.S. and in July 2004 for Canada and Europe; however, Unisys and other companies have patents on different variants of LZW used in other GIF formats/ (Computer Desktop Encyclopedia) (Back to Top)

 

BMP file: (BitMaP file)  Also known as a "bump" file, it is a Windows and OS/2 bitmapped graphics file format.  It is the Windows native bitmap format, and every Windows application has access to the BMP software routines in Windows that support it.  BMP files provide formats for 2, 16, 256 or 16 million colors (1-bit, 4-bit, 8-bit and 24-bit color). BMP files use the .BMP or .DIB extensions (DIB stands for Device-Independent Bitmap). (Computer Desktop Encyclopedia) (Back to Top)

 

EPS (Encapsulated PostScript)  A PostScript file format used to transfer a graphic image between applications and platforms.  EPS files contain PostScript code in ASCII text as well as an optional preview image in TIFF, WMF, PICT or EPSI format (EPSI is also ASCII).  Adobe Illustrator has its own variation of EPS, therefore, both Illustrator EPS and standard EPS files are in use.

The typical use of EPS would be to export an illustration created in a drawing program to an EPS file and to import it into a page layout program.  Using the preview image, the illustration then could be scaled to fit the page design requirements.  The document and embedded EPS images would be saved in the native format of the page layout program (PageMaker, QuarkXPress, etc.) and then printed on a local printer or "printed to disk" as a standard PostScript file for input to an imagesetter.

EPS files are considerably larger than most other graphics file formats; however, since they are text files, they will compress to about a quarter of their original size.  See EPSI.

EPSF (Encapsulated PostScript File)  The full name of an EPS file.  It is used for EPS file extensions in non-DOS and Windows platforms that can handle more than three characters.  See EPS.

EPSI (Encapsulated PostScript Interchange)  A bitmap format used as a preview image in an EPS file.  It contains only 7-bit ASCII data.  It has been used in DOS applications that do not support TIFF, WMF and PICT formats. (Computer Desktop Encyclopedia)  (Back to Top)

 

PSD file: Photoshop's native, layered file format.  The layers enable an illustration to be built with individual graphic elements that can be moved over and over to obtain a desired result.  When the PSD format is converted into a TIFF, JPEG, GIF or other graphics format, the layering is "flattened" into one bitmapped image.  For example, it would be very difficult to build a collage of many images overlapping each other without layers, because the placement of each object would have to be perfect from the start.  Without layers, once a small bitmap is placed on top of the large bitmap, it becomes "one with the image" and cannot be altered at all or at least without major effort. (Computer Desktop Encyclopedia) (Back to Top)

 

PDF file (Portable Document Format file)  An electronic file format from Adobe that has become the de facto standard for publishing brochures, data sheets, white papers and technical manuals on the Web.  In addition, PDF files are based on the same underlying architecture as Adobe's PostScript, which supports complicated page layout.  Thus, like PostScript, the PDF format is widely used to send publications to commercial printers.

Embedded Fonts - Accurate Rendering The PDF document exchange architecture solves a chronic font incompatibility problem, in which the target computer does not have the fonts required by the document.  Unlike Microsoft Word and other word processing formats, and unlike PostScript, PDF files do not rely on the fonts in the computer that displays or prints them.  Document designers are free to choose whichever fonts they have at their disposal, and those fonts are embedded within the PDF file itself.  Because the fonts are embedded within the document and not distributed for general use, font copyrights are not violated, and the page is guaranteed to display and print correctly on any computer with PDF rendering software.  See PDF/X and font incompatibility.

Rendering PDFs: Adobe Reader (formerly Acrobat Reader) is Adobe's free download for displaying and printing PDF files, and hundreds of millions of users have downloaded this software from www.adobe.com.  Adobe Reader lets you view and print a PDF file, but cannot be used to create or edit PDFs.

Creating and Editing PDFs: PDF files are created with Adobe's Acrobat software.  Acrobat can convert a wide variety of document types on Windows, Mac and Unix to the PDF format.  Non-Adobe products are also available for converting to PDF, such as Jaws PDF Creator from Global Graphics Software (www.globalgraphics.com).  Certain applications, such as PageMaker and Illustrator, as well as non-Adobe applications, include PDF converters and can export content to the PDF format. (Computer Desktop Encyclopedia) (Back to Top)